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Gradients in the number of species at reef-seagrass ecotones explained by gradients in abundance.

Tuya F, Vanderklift MA, Wernberg T, Thomsen MS - PLoS ONE (2011)

Bottom Line: Patterns in the number of species, however, can be confounded by patterns in abundance of individuals, because more species tend to be found wherever there are more individuals.Similarly, the abundance of gastropods and species density was higher at edges relative to interiors of Amphibolis meadows, but not in Posidonia meadows.The higher number of species at the reef-Amphibolis edge was therefore a consequence of higher abundance, rather than species richness per se.

View Article: PubMed Central - PubMed

Affiliation: Centro en Biodiversidad y Gestión Ambiental, Marine Sciences Faculty, Universidad de Las Palmas de Gran Canaria, Las Palmas, Canary Islands, Spain. f.tuya@ecu.edu.au

ABSTRACT
Gradients in the composition and diversity (e.g. number of species) of faunal assemblages are common at ecotones between juxtaposed habitats. Patterns in the number of species, however, can be confounded by patterns in abundance of individuals, because more species tend to be found wherever there are more individuals. We tested whether proximity to reefs influenced patterns in the composition and diversity ('species density'  =  number of species per area and 'species richness'  =  number of species per number of individuals) of prosobranch gastropods in meadows of two seagrasses with different physiognomy: Posidonia and Amphibolis. A change in the species composition was observed from reef-seagrass edges towards the interiors of Amphibolis, but not in Posidonia meadows. Similarly, the abundance of gastropods and species density was higher at edges relative to interiors of Amphibolis meadows, but not in Posidonia meadows. However, species richness was not affected by proximity to reefs in either type of seagrass meadow. The higher number of species at the reef-Amphibolis edge was therefore a consequence of higher abundance, rather than species richness per se. These results suggest that patterns in the composition and diversity of fauna with proximity to adjacent habitats, and the underlying processes that they reflect, likely depend on the physiognomy of the habitat.

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Total number of gastropod species on reefs and seagrass meadows with varying proximity to reefs.(a) Posidonia; (b) Amphibolis. The number of shared taxa between reefs and seagrass meadows at varying proximity from reefs is nested (i.e. black bar) inside each bar.
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pone-0020190-g001: Total number of gastropod species on reefs and seagrass meadows with varying proximity to reefs.(a) Posidonia; (b) Amphibolis. The number of shared taxa between reefs and seagrass meadows at varying proximity from reefs is nested (i.e. black bar) inside each bar.

Mentions: A total of 15,368 individuals and 43 species of gastropods were counted on reefs and adjacent seagrass meadows. Five species were unique to reefs, while four species were unique to seagrass meadows. The total number of gastropod species generally declined monotonically from reef edges to the interiors of seagrass meadows (Fig. 1). The total number of shared taxa between reefs and seagrass meadows also declined with increasing distance from reefs, though this decline depended on the dominant seagrass species: reefs and reef-seagrass edges shared a larger number of taxa in Amphibolis meadows (Fig. 1b). The total abundance of gastropods (Fig. 2) was higher on reefs than in seagrass meadows (Table 1; P<0.05 for “Distances” in all cases). Total abundances were higher at reef-seagrass edges (0 m) than in Amphibolis-seagrass interiors (>300 m) (Fig. 2, P<0.05, pairwise comparisons), but not in Posidonia-seagrass interiors (Fig. 2, P>0.05, pairwise comparisons).


Gradients in the number of species at reef-seagrass ecotones explained by gradients in abundance.

Tuya F, Vanderklift MA, Wernberg T, Thomsen MS - PLoS ONE (2011)

Total number of gastropod species on reefs and seagrass meadows with varying proximity to reefs.(a) Posidonia; (b) Amphibolis. The number of shared taxa between reefs and seagrass meadows at varying proximity from reefs is nested (i.e. black bar) inside each bar.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3101235&req=5

pone-0020190-g001: Total number of gastropod species on reefs and seagrass meadows with varying proximity to reefs.(a) Posidonia; (b) Amphibolis. The number of shared taxa between reefs and seagrass meadows at varying proximity from reefs is nested (i.e. black bar) inside each bar.
Mentions: A total of 15,368 individuals and 43 species of gastropods were counted on reefs and adjacent seagrass meadows. Five species were unique to reefs, while four species were unique to seagrass meadows. The total number of gastropod species generally declined monotonically from reef edges to the interiors of seagrass meadows (Fig. 1). The total number of shared taxa between reefs and seagrass meadows also declined with increasing distance from reefs, though this decline depended on the dominant seagrass species: reefs and reef-seagrass edges shared a larger number of taxa in Amphibolis meadows (Fig. 1b). The total abundance of gastropods (Fig. 2) was higher on reefs than in seagrass meadows (Table 1; P<0.05 for “Distances” in all cases). Total abundances were higher at reef-seagrass edges (0 m) than in Amphibolis-seagrass interiors (>300 m) (Fig. 2, P<0.05, pairwise comparisons), but not in Posidonia-seagrass interiors (Fig. 2, P>0.05, pairwise comparisons).

Bottom Line: Patterns in the number of species, however, can be confounded by patterns in abundance of individuals, because more species tend to be found wherever there are more individuals.Similarly, the abundance of gastropods and species density was higher at edges relative to interiors of Amphibolis meadows, but not in Posidonia meadows.The higher number of species at the reef-Amphibolis edge was therefore a consequence of higher abundance, rather than species richness per se.

View Article: PubMed Central - PubMed

Affiliation: Centro en Biodiversidad y Gestión Ambiental, Marine Sciences Faculty, Universidad de Las Palmas de Gran Canaria, Las Palmas, Canary Islands, Spain. f.tuya@ecu.edu.au

ABSTRACT
Gradients in the composition and diversity (e.g. number of species) of faunal assemblages are common at ecotones between juxtaposed habitats. Patterns in the number of species, however, can be confounded by patterns in abundance of individuals, because more species tend to be found wherever there are more individuals. We tested whether proximity to reefs influenced patterns in the composition and diversity ('species density'  =  number of species per area and 'species richness'  =  number of species per number of individuals) of prosobranch gastropods in meadows of two seagrasses with different physiognomy: Posidonia and Amphibolis. A change in the species composition was observed from reef-seagrass edges towards the interiors of Amphibolis, but not in Posidonia meadows. Similarly, the abundance of gastropods and species density was higher at edges relative to interiors of Amphibolis meadows, but not in Posidonia meadows. However, species richness was not affected by proximity to reefs in either type of seagrass meadow. The higher number of species at the reef-Amphibolis edge was therefore a consequence of higher abundance, rather than species richness per se. These results suggest that patterns in the composition and diversity of fauna with proximity to adjacent habitats, and the underlying processes that they reflect, likely depend on the physiognomy of the habitat.

Show MeSH